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Very intense mesoscale or synoptic-scale rainfall events can occasionally be observed in the Mediterranean region without any deep cyclone developing over the areas affected by precipitation. In these perplexing cases the synoptic situation can superficially look similar to cases in which very little precipitation occurs. An example is the major precipitation and flooding event that affected Piedmont, Italy, between 13 and 16 October 2000. The emphasis of this study is on the moisture origin and transport. Moisture balances are computed on different space and time scales, revealing that precipitation exceeds evaporation over an area inclusive of Piedmont and the northwestern Mediterranean region, on a time scale encompassing the event and about 2 weeks preceding it. This is suggestive of an important moisture contribution originating from outside the region. A synoptic and dynamic analysis is then performed to outline the potential mechanisms that could have contributed to the large-scale moistur...

This paper illustrates some applications of COSMO-SkyMed (CSK) observations for rapid mapping of flooded areas and damages in small to medium size catchments. The results presented here have been obtained within the framework of the project “OPERA — Civil protection from floods” funded by the Italian Space Agency and run by a team of scientific research centres and private companies. The project aims to the systematic evaluation of the added value of the use of Earth Observation techniques into operational flood prediction chains. Due to the specific geomorphology of Italy, the focus is mainly on flash floods on small sized river catchments. Monitoring and modelling processes at proper space-time scales in this environment raise several issues to be solved, compared to applications in larger river basins. Here we address some related to the suitable use of CSK imagery.

The COSMO-SkyMed mission is expected to give a fundamental contribution for flood mapping, because of the high revisit time and throughput achieved by the four satellites that form the constellation. To study the potentiality of COSMO-SkyMed radar data for this purpose, two inundation events are analyzed in this paper, namely the flood occurred in Myanmar in May 2008 and the event that took place in the city of Alessandria (Italy) in April 2009. For the first event, two radar images were considered, one temporally close to the peak of the event, and the other one acquired one week later. As for the Alessandria flood, a time series of images was available, so that an attempt to monitor the temporal evolution of the inundation was accomplished.

Development of an operational flood forecasting system and assessment of forecast uncertainty are the principal topics of this paper. Flood forecasting procedures are developed for a Mediterranean environment. A procedure that uses the Ensemble Prediction System as input for a semidistributed hydrologic model is presented. A rainfall downscaling model is used to bridge the scale gap between numerical weather prediction model output and hydrologic modeling input. The results are illustrated for the November 1994 Piedmont flood.

The Po river drains the largest morphological unit of the Italian territory. River training works started in the lower Po during the Roman Age and developed upstream, first as discontinuous systems, then connected to form two uninterrupted belts, which have reduced the overflow frequency but also the storage capacity of the river flood bed. The outcome is an increasing value of the flood peak with given probability in the lower Po, which is the reach with the higher flooding risk. On the other hand, the upstream catchment, in which the river is provided with partial embankments, recently experienced a flooding event and require some form of protection. A risk mitigation policy should perceive and take into account all the components of the river system and their connections. In this perspective the development of traditional structural protection along the Po river has reached a critical stage; a further expansion of the existing levee system increases the down-stream risk. From the viewpoint of non structural protection, the river morphology and the past experience suggest that, based on rainfall and discharge monitoring, early warnings of flood hazards can be provided to communities that could be affected by such occurrences. Finally, to reduce the flooding risk in the lower Po a reduction of the flood discharge entering this reach is needed. This can be obtained by diverting the higher part of the flood from the river immediately upstream of the lower Po, allowing the inundation and the temporary storage of the diverted water on pre-designed large agricultural areas. Implementing such a policy will require a reliable system of flood warning and, above all, a sound regulatory authority.

A review of some recent applications of “hydrologically oriented” GIS in flood forecasting and related issues is presented. A regional approach to the assessment of flood hazard in orographically accentuated areas is also described on the basis of the supporting data handling capabilities of Geographical Information Systems. In particular, the development of operational methodologies aimed at the issuing of effective and timely warnings at the regional scale is presented both in a deterministic perspective — by simple enumeration of a series of pre-defined targets — and in a probabilistic one, based on the most recent advances in drainage geomorphology. The use of multisensor monitoring devices for the detection of extreme events, from the overall meteorological scenario down to the scale of the local variability of rainfall in space, is proposed on the basis of the experience of some international research projects recently activated in the field. The multi-faceted role of GIS in the collection of rainfall data from the whole set of available sensors, the identification of areas of potential occurrence of extreme meteorological events, the operational support to distributed rainfall-runoff models and the mapping of flood prone areas and landscape vulnerability is highlighted throughout the paper.

In the streets of Florence in the thirteenth century, though prohibited by law, dice players used to shout “zara” when the total value of the three dices rolling over the table showed the lowest probability sets of results (less than or equal to seven, or greater than or equal to fourteen, meaning “null try”): “quia cum tribus taxillis raro veniunt sex vel quinque et rarius quator vel tria...eodem modo accidit inter quator decim et decern octo” (2). From the arabic “azzahr”, the dice, the sense of rare events, not involving any special connotation of danger or risk, came into French as “hasard”, into Italian as “azzardo” and into English as “hazard”.

The event of November 23–25th, 1987 on the Arno basin was observed by ground raingauges and a hydrometric reporting network, the Meteosat geosyncronous satellite, and the Special Sensor Microwave/Imager (SSM/I) aboard a polar orbiting satellite. In the present paper the three data sets derived from the different information sources are used as an input to a coherence assessment analysis; information provided by raingauges, geosyncronous and polar satellites are indeed intrinsecally different as far as space and time scales and reliability are concerned. The proposed approach has two main purposes: i) to integrate effectively different data sources to obtain a rain rate estimate which minimises the overall deviation from the set of available measurements; ii) to assess the relative reliability of a source with respect to the others. Hydrographs in Florence at Uffizi, simulated by a distributed model using the Meteosat information and raingauge data, have been compared to the observed one in order to assess the use of multisensor observations to predict rainfall ground effects during the considered extreme meteorological event.

The right of a person to be protected from natural hazards is a characteristic of the social and economical development of the society. This paper is a contribution to the reflection about the role of Civil Protection organizations in a modern society. The paper is based in the inaugural conference made by the authors on the 9th Plinius Conference on Mediterranean Storms. Two major issues are considered. The first one is sociological; the Civil Protection organizations and the responsible administration of the land use planning should be perceived as reliable as possible, in order to get consensus on the restrictions they pose, temporary or definitely, on the individual free use of the territory as well as in the entire warning system. The second one is technological: in order to be reliable they have to issue timely alert and warning to the population at large, but such alarms should be as "true" as possible. With this aim, the paper summarizes the historical evolution of the risk assessment, starting from the original concept of "hazard", introducing the concepts of "scenario of event" and "scenario of risk" and ending with a discussion about the uncertainties and limits of the most advanced and efficient tools to predict, to forecast and to observe the ground effects affecting people and their properties. The discussion is centred in the case of heavy rains and flood events in the North-West of Mediterranean Region.

In the perspective of flood hazard multisensor monitoring, the event of 4–6 November, 1994 over Northern Italy is described and analyzed in this paper using traditional ground‐based rainfall observations and remote sensing techniques. Satellite imagery is used with different objectives: the interpretation of SAR measurements allows the identification of flooded areas, Meteosat infrared images show high intensity rain areas and SSM/I passive microwave data provide estimates of the rain‐rates. The IFA‐SAP algorithm, a profile based retrieval technique for estimating rainfall rates and precipitating cloud parameters from spacebome multifrequency microwave radiometers, has been used in the latter case. The use of multisensor observations considerably supplements conventional monitoring systems which prove inadequate for many hydrological purposes. The present paper is written in the spirit of encouraging a posteriori analyses of observed heavy rainfall events so as to explore the potential of a real‐time oper...